The invention relates to apparatus for forming a transition joint between pieces of copper and aluminum; and more particularly, relates to apparatus for cold welding copper and aluminum transition joints in a relatively continuous, high volume manner that consistently affords reliable transition joints of good quality.
Heretofore, numerous attempts have been made to develop machinery for suitably cold welding, or otherwise fastening together, wires or bar stock of copper and aluminum in order to provide transition joints between systems utilizing these two relatively common metals. The need for suitable copper-aluminum transition joints is particularly great in various facets of the electrical connector industry in which it is common to encounter interconnected circuits using both of these metals. However, in addition to creating a strong demand for such transition joints, the environment in which many electrical circuits are utilized presents particularly difficult application problems insofar as the necessary characteristics of such transition joints are concerned. For example, it has been found that copper-aluminum transition joints used to make electrical connections between aluminum motor windings and copper power distribution circuits to which the windings are coupled are very likely to fail due to thermal cycling and mechanical vibration of the joints, if the joints do not, in fact, meet a high standard of quality and reliability. Such prior art problems and one optimum solution to them are described at some length in co-pending U.S. patent applications Ser. Nos. 591,833 and 591,838 which were both filed on June 30, 1975 and are assigned to the assignee of the present invention.
As is pointed in those applications, it has been found to be particularly desirable to form copper-aluminum transition joints for electrical circuit application by a method that results in a cold-weld intermetallic connection being formed between the joined copper and aluminum pieces. The present invention is directed toward an apparatus for reliably making such cold-welded transition joints on a high volume production basis suitable for mass production end uses of the connector joints.
In view of the large number of earlier attempts that have been made to manufacture suitable copper-aluminum transition joints, obviously a wide variety of types of connector manufacturing apparatus has already been developed by others. Typically, such apparatus simply utilizes die means to crimp or otherwise mechanically deform the bar stock or wire that is to be jointed together to form a suitable transition joint. One example of such a relatively common die means is shown in U.S. Pat. No. 3,708,878, which issued on Jan. 9, l973. Known prior art apparatus such as that exemplified by the foregoing patent has, of course, been generally suitable for manufacturing simple bi-metal transition joints in which it is not imperative that a uniform intermetallic cold welded junction of high mechanical and electrical integrity be formed. However, when copper-aluminum transition joints are to be used in those electrical circuit environments that subject the joints to severe thermal cycling and extensive mechanical vibration such as that produced by electric motors, as described in the above-mentioned co-pending patent applications, it has become necessary to develop an apparatus for more rapidly forming transition joints of greater uniform quality and reliability than has been available heretofore.
A primary object of the present invention is to provide an apparatus for forming aluminum-to-copper transition joints that overcome the above-mentioned disadvantages of related prior art apparatus.
Another object of the invention is to provide a copper-aluminum transition joint forming apparatus that affords a relatively continuous, high speed means for producing electrically and mechanically reliable transition joints on an economical basis.
Additional objects and advantages of the invention will be apparent from the description of it that follows considered in conjunction with the attached drawings.